This invention relates to fungicides and is intended particularly to provide a fungicidal composition and/or a method of preparing a fungicidal composition, particularly but not exclusively for application to lignocellulosic substrates so as to confer an antifungal characteristic to logs, lumber or other products derived from said lignocellulosic substrates and to other organic substrates such as leather products and paint.
Whilst still alive and growing, trees, suitable for conversion to lumber or other lignocellulosic products, are relatively immune from or are self protecting against fungal attack. After felling logs are immediately vulnerable to attack due to cutting or bark damage due to colonisation by fungi. Damage to the substrate initially appears as visual degrade (due to pigment formation by the fungi) which lowers the value of the substrate but later this may also lead to physical degrade which may negate the value of the substrate. To protect these or products derived from them from degradation it is common practice to treat these with aqueous fluids containing fungicides (biocides).
Historically a wide range of fungicides has been used including toxic substances such as sodium pentachlorophenate, trichlorophenol, and mercury compounds. Modern prophylactic formulations generally use less toxic compounds although those more toxic are still used in some cases. Often when cost is a major consideration, and more so in less developed countries, more hazardous compounds continue to be used. Where cost is an issue, a more competitive formulation will offer a viable option.
More recently the lumber industry has been looking closely at prophylactic formulations to further reduce any potential threat and in doing so has been scrutinising formulating aids typically used in these formulations. Some concern is evident regarding certain solvents, and other additives have been recognised as posing a threat to workers using these products.
Traditionally prophylactic treatment formulations have been formulated such that they, by design or default, adhere to, fix to or precipitate at the surface of the substrate.
For example, one of the earlier biocides used, pentachlorophenol was formulated at a high pH, as the sodium salt of the otherwise relatively insoluble pentachlorophenol. Upon application to the substrate as an aqueous solution the pentachlorophenol would precipitate due to the buffering action of the wood which has a natural pH of approximately 4.0. Although highly toxic, pentachlorophenol did have an advantage over most modern biocides in that it has a high vapour pressure so was able control fungal degrade remote from the point of application by fumigant action.
U.S. Pat. No. 4,950,685 to Kop-Coat teaches the formulation of a synergistic prophylactic formulation comprising dodecyl dimethyl ammonium chloride (DDAC) and iodo propynyl butyl carbamate (IPBC) as co-biocides. In this case, for example, when applied to wood, DDAC will fix to the wood surface by an ion exchange mechanism and since the DDAC, which acts as a surfactant solubiliser for the IPBC, has been deactivated by binding to the substrate, the IPBC, which has low solubility in water, precipitates at the surface also.
U.S. Pat. No. 1,571,814 to Chapman Chemical teaches the solubilisation of copper 8-hydroxyquinolinolate using various strong organic acids. The biocides of this invention have good efficacy and are relatively inexpensive. The acids used however are corrosive to metals that may be involved in the containment of the formulations during use, add significantly to cost, cause foaming (which is inconvenient and potentially hazardous) and may be toxic to workers exposed to the product. The mechanism of fixation in this instance also relies on the natural buffering pH of the substrate (4.0) wherein the treating solution with a pH normally around 2.5 to 3 will precipitate the copper 8-hydroxyquinolinolate when the pH increases to 4.0 on the substrate surface. It has been well documented that copper 8-hydroxyquinolinolate completely precipitates when the pH is greater than 3.3 (Arthur I. Vogel. A Text-book of Quantitative Inorganic Analysis, Third edition 1966 Longmans).
Similarly NZ Patent 225428 to Chemicca describes an organic solvent based formulation combining copper 8-hydroxyquinolinolate (frequently referred to in the art as xe2x80x9coxine copperxe2x80x9d) and carbendazim (methyl benzirnidazoyl carbamate) using dodecyl benzene sulphonic acid as a solubilising agent. The principle of solubilisation and precipitation of this formulation is the same as that of U.S. Pat. No. 1,571,814 except that carbendazim requires higher levels of acid to solubilise the additional biocide. This leads to an additional disadvantage for this type of formulation in that it is more expensive and in that the carbendazim precipitates more readily. This occurs where contamination of the treating solution occurs with natural salts from the source of water, or chemicals from the wood itself leach into the treating solution, raising the pH to a point where the carbendazim begins to precipitate prematurely. This leads to agglomeration of carbendazim particles and, and eventually to changes in the rheology of the solution making the product difficult to use and in some cases, for example, when it may be sprayed, impractical to use. The formulating aids used in this type of formulation are costly and also impose an additional biological load on the environment. Foaming of the product in use is frequently a problem.
Many other products have been produced for this market including suspension concentrates or flowables wherein the insoluble biocides are ground to a very small particle size (less than 10 microns) and then stabilised in suspension using various aids. These formulations are expensive to produce but more significantly precipitate during use necessitating continuous vigorous agitation, and are precipitated at the wood surface by a filtering action.
It is now being more widely recognised that certain fungal species, which colonise wood and derivatives, grow remarkably rapidly (for example many of the Ophiostoma species) and can penetrate into the substrate from the surface at an easily detectable rate. Wood and many other natural products are very rarely treated with prophylactic materials at the time of initial production and therefore may be well colonised by degrading organisms before any biocide is applied. It is therefore logical that these organisms may be well out of reach of, and therefore are unable to be controlled by, any biocide that precipitates or remains very close to the surface of the substrate. This is now well recognised by those working in the industry. Historically pentachlorophenol and trichlorophenol were able to achieve a level of control by the fumigant action previously mentioned.
Unfortunately pentachlorophenol and trichlorophenol have generally been prohibited from use due to its high toxicity. Few other fungicides have a similar action and those that do are also acutely toxic such as methylene bis-thiocyanate.
There is a need therefore for a prophylactic treatment system that allows the biocide or biocides to penetrate further into the substrate prior to precipitation. Very strong acids can be used to dissolve many of these biocides but they are hazardous, can destroy the wood substrate and will certainly aggravate any corrosivity.
Although preferred fungicidal actives are now being chosen from a group having very low toxicity, other components still pose problems. These include those used in the aforementioned patents and can be summarised to include;
high toxicity to users (by ingestion, skin contact or inhalation)
high levels of irritation
strong offensive odour
corrosivity to metals
high levels of foam formation
poor physical properties leading to improper application such as:
high viscosity
precipitation and agglomeration of actives
a poor rheology leading to poor spraying
loss of actives during recovery and recycle.
Formulating aids that have been used to solubilise biocides include toluene sulphonic acid, benzene sulphonic acid, dodecylbenzene sulphonic acid, and lactic acid, amongst others. Typically dodecylbenzene sulphonic acid (DDBSA) has been used which has the disadvantage of being quite toxic, irritant, corrosive to metals, causes foam formation and which poses a biological load to the environment.
Whilst solubility of biocides at high concentrations in aqueous systems and stability at such concentrations is important in the preparation of stable formulations for temporary protection of wood or other substrates, the low final use rate concentrations can tolerate higher manufacturing and distribution costs.
It is more critical in the preparation of biocide formulations for permanent preservation of lumber that all costs be minimised because quite high loadings of biocides are impregnated into the lumber.
For example, two proven preservatives for the permanent preservation of wood include Copper Chrome Arsenate (CCA) and oxine copper.
CCA is prepared by dissolution in water of a mixture of copper, chromium and arsenic compounds. These typically include cupric oxide, chromium trioxide and arsenic pentoxide. This mixture is clearly highly toxic. The formulation is shipped at a concentration of approximately 60 per cent to minimise the impact of the freight cost on the final delivered price. Whilst this type of preservative is highly toxic it can be shipped in high volumes to remote treatment plant sites competitively.
CCA is an extremely effective permanent preservative for lumber and can be produced cost effectively. The major disadvantages of CCA are;
toxic and hazardous to produce
hazardous to use
long term environmental impact of waste when treated lumber is retired from service
Oxine copper is a biocide with low toxicity (cf Oral LD50 Rat 10,000 mg/kg versus arsenic LD50 Rat 15-293 mg/kg and which is also carcinogenic).
Oxine copper has until this invention was developed been formulated in two principal ways.
(A) solubilised in complex solvent systems with metal soaps such as Nickel Hexanoate added as solubilising agents. (The concentration of oxine copper is generally 10 per cent or below because this is near the limit of solubility. Consequently the formulation is expensive to formulate, freight and use. This restricts commercial acceptability to use for treatment of lumber for more critical areas such as food contact use or playground equipment for children),
(B) solubilised in dodecylbenzene sulphonic acid with a co-solvent such as propanol or ethylene glycol. (The concentration of oxine copper is 10 per cent or below because this again is near the limit of solubility. Also, at this concentration the product becomes very viscous and difficult to handle. The high level of formulating aids required to achieve this concentration makes this product uncompetitive for permanent preservation of lumber).
We have carried out many solubility studies using the technology of this invention. For example, we are able to produce solutions stable at ambient temperature of oxine copper at concentrations greater than 100 grams per 200 mls of final product. Because the specific gravity of such solutions is approximately 2.8 this yields a solution of oxine copper of 50 per cent weight/volume or more. This concentration is commercially viable to use and eliminates many of the potentially toxic or flammable formulation aids used in prior art solubilisation of oxine copper.
Oxine copper is approved for use in permanent preservation of lumber (US AWPA P8-95) at 0.02 pounds per cubic foot (0.32 kilograms per cubic metre) compared to CCA at 0.25 pounds per cubic foot (4.00 kilograms per cubic metre) for a similar end use. Because the use rate for this biocide in permanent preservation of wood is lower than CCA and because we can produce stable highly concentrated solutions we can minimise the impact of manufacturing, packaging and freight costs on the delivered price. This is anticipated to enable the competitive use of oxine copper (a low toxicity biocide) in situations where otherwise highly toxic CCA would be used. Further benefits accrue from the use of the technology of this invention. Since the required retention of biocide is significantly lower than CCA the total mass of biocide used by industry may be decreased by an order of magnitude. Not only is this essential and beneficial during use of the biocide, it is also significantly more important when the lumber is retired from service in which case oxine copper treated lumber exposes very low levels of heavy metals to the environment compared to CCA which will release copper, chromium and arsenic in large amounts.
It is important also that the preservative be a stable solution in both concentrated form and when diluted for application such that the end use solutions can be reused if surplus during a treatment process or may have further water and biocide concentrate added for make up and reuse. This invention because of the specific acid used and the high solubility and stability of the resultant solutions is able to achieve this requirement previously unachievable.
The present invention relates to fungicides and is intended particularly to provide a fungicidal composition and/or a method of preparing a fungicidal composition, for application to lignocellulosic or proteinaceous substrates so as to confer an antifungal characteristic to logs, lumber or other products derived from said lignocellulosic substrates or hides or leather substrates, wherein preferably the biocides are truly solubilised and maintained at a pH which provides stability as a concentrate and also as a working solution and also where said formulation offers additional mobility to said biocides such that they may be active at a point remote from that of application.
In a first aspect the invention is a biocidal composition being in the form of
(1) a solution carried by a liquid selected from the group consisting of water and polar solvents, or
(ii) as a solids mix soluble in a liquid solvent selected from the group comprising water and polar solvents,
said composition having
a source of free phosphite ions selected from the group comprising phosphorous acid and phosphite compounds capable of releasing phosphite ions at a pH of below 4 and at the pH of the true solution hereinafter referred to, and
at least one biocide,
wherein, as a true solution in the presence of said liquid, the pH is or will be below 4.
Preferably said composition is an antifungal composition and/or an antibacterial composition.
Preferably water is present.
Preferably said liquid is at least primarily water.
Preferably said liquid is water.
Preferably phosphorous acid is the source of the phosphate ions.
Phosphorous acid is the preferred acid because it is a very strong acid (stronger than phosphoric acid), it has biocidal properties and in some instances it is synergistic with biocides of this invention.
Use of phosphoric acid is not preferred because it produces inferior biological performance, an unstable composition and makes no biocidal contribution.
The solvent (ie; the liquid) is preferably water for reasons of cost and flammability but could include lower alcohols (methanol, ethanol or propanol), or other solvents such as glycols, glycol ethers, glycol esters, cyclic lactams or cyclic lactones, ketones and others and mixtures thereof.
Preferably said at least one biocide is stable at a pH below 4 or said biocide or biocide precursors form or become stable biocide(s) as the pH of the use strength solution rises to a pH of 4.
Preferably the pH is or will be below 3.
Preferably the pH is or will be below 2.5.
Preferably said at least one biocide is selected from the group comprising benzimidazoles, precursors of benzimidazoles, substituted morpholines, organic chelate complexes of metals, precursors of such organic complexes of metals, metal ions selected from the group consisting of Al, Co, Cu, Mn, No, Ni, Wo, Va and Zn.
Preferably a benzimidazole is present.
Preferably said biocide is a said organic chelate complex of a metal.
Preferably said organic chelate complex is of an 8-hydroxyquinoline.
Preferably the metal is copper or zinc and the complex is an oxine of copper or zinc cations with 8-hydroxyquinoline.
Preferably said cations are of copper (ie; copper oxine).
Preferably phosphorous acid and/or any other source of phosphite ions is or are in a stoichiometric relationship to the biocide(s) to the extent required to ensure at least substantially fill solubility of the biocide(s) in said liquid.
Preferably phosphite ions are present and the hydrogen ion concentration from the source of phosphite ions or other acid contribute to a pH below 4.
Preferably phosphorous acid is or has been present and is in a stoichiometric relationship to copper oxine such that at least substantially all of the copper oxine is in solution.
Preferably phosphite ions are present and the hydrogen ion concentration from the source of phosphite ions or other acid contribute to a pH below 4.
In another aspect the present invention consists in an antifungal composition in the form of a solution comprising
oxine copper (ie; a copper cation complex with 8-hydroxyquinoline), phosphorous acid, and
water, the pH being less than 4.
Preferably the pH is less than 3.
Preferably the pH is about 2.5 or less.
Preferably another biocide is present in solution.
Preferably as a wood preservative wherein, in time, at the pH of wood, said at least one biocide will fix in the wood from the lower pH solution.
Preferably the biocidal composition contains a stable highly concentrated solution of biocidal.
Preferably the biocide is a metal chelate of the precursors thereof Preferably the metal chelate is a metal chelate of oxine (8-hydroxyquinoline) or a mixed chelate thereof or the precursors thereof; more preferably the metal chelate is oxine copper or the precursors thereof.
In still another aspect the invention consists in an antifungal composition comprising or including;
phosphorous acid, and
at least one acid stable biocide selected from the group comprising
benzimidazoles which are stable in acid conditions,
precursors of benzimidazoles,
substituted morpholines which are stable in acid conditions,
organic chelate complexes of metals, and
precursors of such organic chelate complexes of metals, and water and/or other polar solvent(s).
Where phosphorous acid is used to solubilise acid stable biocides to produce formulations (preferably which contain a stoicheiometric excess of phosphorous acid;) active ingredient concentrations of greater than 5 per cent biocide by weight and phosphorous acid preferably greater than 5 per cent by weight (more preferably greater than 10 per cent biocide by weight) are used.
Active ingredients include but are not restricted to; metal chelates or one or more precursors thereof, Fenpropimorph and other substituted morpholine fungicides, Carbendazim and other benzimidazoles, metal phosphites and/or metal ions including but not restricted to those of copper, zinc and aluminium and/or other acid stable fungicides.
In another aspect the present invention consists in an antifungal composition at least having an acid stable biocide(s) solubilised in a liquid system at a pH below 4.0 such that, upon delivery into a matrix, for example wood or leather, rising pH conditions over time will lead to the fixing of the acid stable biocide(s).
Preferably acid stable biocide(s) or biocide or biocide precursors which form or become stable biocide(s) as the pH of the use strength solution rises to a pH of 4, said composition being subjected to treatment with a pH increasing solution to facilitate fixing of the biocide(s).
Preferably said pH increasing solution contains further biocide(s).
Optionally present is a latent buffer which will raise the pH of the solution over time to facilitate fixing of the biocide(s).
Preferably the composition is applied to a substrate where a latent buffer will raise the pH of the solution over time to facilitate fixing of the biocide(s).
Preferably the acid stable biocide(s) or biocide or biocide precursors which form or become stable biocide(s) as the pH of the use strength solution rises to a pH of 4 is supported in phosphorous acid which optionally may include water and/or other polar solvent(s).
In another aspect the invention consists in an antifungal and/or antibacterial composition which is a true solution (or soluble concentrate) comprising or including;
at least one biocide selected from the group comprising benzimidazoles, precursors of benzimidazoles, substituted morpholines, organic chelate complexes of metals, precursors of such organic complexes of metals, metal ions (Al, Co, Cu, Mn, Mo, Ni, Wo, Va and Zn), and other acid stable fungicides,
free or mobile phosphite ions (ie; phosphite ions in solution, not as undissolved metal or organic phosphates) and,
water and/or other polar liquid miscible with water,
and wherein the composition has or, in the presence of water, will have a pH less than 4.0
Preferably phosphite ions have been provided by phosphorous acid.
Preferably phosphite ions are sourced from the addition of a strong acid to a phosphite salt.
Preferably sufficient hydrogen ions are present to ensure the pH of the solution is below 4.
Preferably the phosphorous acid is in stoichiometric excess of the biocide(s).
In another aspect the invention is a method of forming a biocidal composition (i) being in or to be in the form of a solution carried by a liquid selected from the group consisting of water and polar solvents or (ii) as a solids mix soluble in a liquid solvent selected from the group comprising water and polar solvents, said composition having a source of free phosphite ions selected from the group comprising phosphorous acid and phosphite compounds capable of releasing phosphite ions at a pH of below 4 and at the pH of the true solution hereinafter referred to, and
at least one biocide,
wherein, as a true solution in the presence of said liquid, the pH is below 4,
said method comprising any one of the following
(20) admixture of the individual composition components and mixing to provide dissolution to produce the solution,
(21) addition of biocide precursors as in (a) with remaining composition components to form the solution,
(22) admixture for components prior to addition of water or polar solvent with subsequent addition of water or polar solvent to form the solution.
(23) addition of biocide precursors as in (b) with remaining components prior to addition of water or polar solvent with subsequent addition of water or polar solvent to fore the solution,
(24) admixture of the individual composition components and mixing to form the solution with subsequent addition of further biocide components, and
(25) admixture of the individual composition components with subsequent addition of a source of hydrogen ions to reduce the pH of the composition to below 4 to form the solution.
In another aspect the invention consists in a method of treating a substrate which comprises applying to such substrate an effective amount of a biocidal composition as previously defined.
Preferably said substrate has a pH above that of said u solution in the presence of said liquid.
Preferably said substrate is wood.
In still a further aspect the present invention consists in the use of a (phytotoxic) antifungal composition in accordance with the present invention, in particular a method of use of such composition wherein;
the composition is applied to a substrate (eg: by dipping the substrate in the composition or a solution of the composition, spraying the substrate with the composition or a solution of the composition, brushing the substrate with the composition or a solution of the composition, and/or treating the substrate with any variation of vacuum and/or pressure cycles applied to the substrate surrounded by the composition or a solution of the composition)
and whereupon, subsequent to the application of the composition, the biocide is allowed to precipitate on or in the substrate due to an increase of pH provided by chemical action on or within the substrate.
Since the composition is usually phytotoxic because of the low pH it should be applied preferably to substrates which do not suffer from such phytotoxicity. This precludes application to living plants.
The preferred substrate to be treated is a substrate which may suffer from visual or physical degrade by organisms namely fungi or bacteria and could include wood, concrete, leather, painted surfaces or any other solid substrate and may include liquid for example, water in cooling towers wherein subsequent to application the biocide is immobilised by precipitation caused by an increase in pH and wherein such pH is caused by alkalinity of the substrate or by a pH buffering action of the substrate.
The preferred substrate is a lignocellulosic material which can include wood, composite board, chips or fibre or animal hides (including leather).
The most preferred substrate is freshly felled and debarked logs and freshly sawn lumber.